I've been an enthusiastic reader of all the Twilight Saga books, and have enjoyed all the movies (even New Moon - criticised by many for what was only its faithfulness to the book). The Breaking Dawn novel blew me away: the best and strongest of the lot, harrowing and exhilarating to read; and I couldn't imagine how they would be able to film it in anything like the same spirit - especially the graphic horror of Renesmee's birth, which I know has been a step too far for some; and equally difficult, the culmination of Edward and Bella's vampire-and-mortal love.
I needn't have worried. The movie did the best possible job of filming the unfilmable in the only sensible way, by sketching these awesome moments in quick flashes that anyone familiar with, and appreciative of, the books would follow without difficulty. Marvellous! Even more than I had dared to expect.
At this point, unsympathetic reviewers (and the "haters", who only contribute to spread a little venom on something they've never liked) say, "But what about people who haven't read the books?" To which I'd reply, "Then go read them, and give them a proper chance; and THEN go see the movies again. If you still don't like the books, then don't presume to comment on something you'll never understand."